Part II: Species Accounts180
districts, as far southeast as Parit Raja] in the month of June, and
they come in successive ‘waves’, each consisting of a very large
number of pigs. By the end of November, however, they have all
disappeared.
Hislop (1955) additionally writes that in July 1953, ‘a large
cohort of these pigs appeared near Kampung Denai on the
Endau River [e.g. modern day Endau-Rompin National Park]
en route from Pahang to Johore’, corroborating the previous
account. Hislop (1955) also notes that the now-extinct bearded
pigs on the western coast of Peninsula Malaysia did not migrate
(e.g. the Sungei Bernam swamps in the Selangor–Perak bor-
der). Other sources also indicate annual and interannual move-
ments, but with substantially less sizable sounders as in Borneo
(Medway 1977).
An important question for future research is the extent to
which either resident or nomadic/migratory bearded pigs will
forage on plantation fruits. For example, the palm oil that has
replaced forest through a large proportion of the pigs’ historic
range contains plentiful fruit year-round (Luskin & Potts 2011).Reproduction and Growth
Fruit supply is a major factor in determining growth rate, fat
deposition, and reproduction, with the typical non-mast food
supply only permitting slow growth (Meijaard 2000). However,
with plentiful fruit during mast years, bearded pigs are capable
of incredible population eruptions that rival the reproductive
rates of any large mammal. Females reach sexual maturity at
10–12 months, have gestation periods of 90–120 days, and typi-
cally have litters of 7–9 piglets. However, litter size is a function
of body size and condition, with larger sows often having litters
of 12, and gestation period varies with the mothers’ condition
and available resources. Females build large nests of saplings,
seedlings, and foliage and give birth in the nests. Piglets remain
in the nest for 3–5 days, and mothers can be receptive to mating
again thereafter. During masting periods a female will raise two
to three litters in a single year, adding an astounding 10–30 new
pigs per year. In Sumatra, bearded pigs may time their repro-
duction around resource availability, as evidenced by juveniles
being first recorded two weeks before the annual durian (Durio)
fruiting season (Linkie & Sadikin 2003). The timing of repro-
duction to correspond with fruit availability is also likely in
Peninsular Malaysian populations, but there are few records to
test this.Behaviour
Little is known about bearded pig social behaviour and mat-
ing (Figure 18.3). It is also unclear if bearded pigs aggressively
compete with other species, such as wild boars, although it is
known that they will aggressively defend their young (Caldecott
1991). While herding behaviour is often an anti-predation tactic
among mammals, it is unclear if this is a primary motivation for
bearded pigs, which lack many predators. In Peninsular Malaysia
and Sumatra tigers are certainly capable of taking adult bearded
pigs, but it is unclear if Borneo’s clouded leopards would risk
injury to attack an adult bearded pig. Based on their population
fluctuations coinciding with fruit availability, bearded pigs arecertainly ‘bottom-up’ regulated, so their herding behaviour is
due to shared instinct to find patchily distributed food, and not
anti-predator strategies such as herding in the plains of Africa
(Fryxell et al. 2014).Parasites and Diseases
Bearded pigs are closely related to the sympatric wild boar
(S. scrofa) and domestic pigs (S. scrofa domesticus) that carry a
variety of diseases, and are thus likely also susceptible or car-
riers of many of these (Lucchini et al. 2005). During Southeast
Borneo’s cattle rinderpest epidemic in 1872, 1878, and 1894
there were reports of the disease spreading to bearded pigs
over large parts of Borneo (Meijaard 2015). Likewise, because
the bearded pig is actively hunted and consumed in Borneo,
bearded pigs are likely vectors of zoonotic diseases for humans.
In 1999, wild boars and domestic pigs were the primary vector
for the Nipah virus jumping between forest bats and people in
Malaysia and Singapore, and bearded pigs may also act as a vec-
tor for zoonotic diseases (Chua 2003). A wide range of endo-
and ectoparasites have been observed on hunted animals (M.S.
Luskin, personal observation), but this has not been formally
researched.Status in the Wild
Bearded pigs are threatened by habitat loss (deforestation)
throughout their range (Figure 18.1). South East Asia leads
the world in deforestation rates, and in Sumatra, less than
25 per cent of the historic forest area remains (Miettinen et al.
2011; Margono et al. 2012). Conserving bearded pigs requires
preserving their various seasonal habitats and their ability to
reach forested areas. Conservation could be best accomplished
by retaining extensive continuous forests that cover swamps,
lowlands, and high elevation hill forests. Unfortunately, such
expanses no longer exist within the bearded pig range; the lack
of such areas has led to their precipitous decline in many places.
The most extreme example is Peninsular Malaysia, where defor-
estation peaked decades before Sumatra or Borneo, and which
has seen bearded pig range and population size contract by over
80 per cent within the last 60 years. However, because Peninsular
Malaysia still retains > 35 per cent forest coverage, the primary
factor explaining bearded pigs’ decline is the fragmentation of
historically important resources. For example, deforestation for
tree plantation crops, roads, and fences in the lowlands has even
separated the peninsula’s largest continuous forest of Taman
Negara National Park from the coastal swamps and mangroves.
As a result, Taman Negara has not had a bearded pig sighting in
over 20 years, nor has the Krau Wildlife Reserve, another large
but isolated forest.
In Sumatra, our analyses of bearded pigs’ current distribu-
tion within remaining forest areas indicates a range contraction
of > 50 per cent in the last 25 years. Only KSNP may have the con-
tinuous habitat from coastal areas to mountains necessary for
bearded pigs’ long-term persistence. Riau province’s remaining
lowland and swamp forests contain healthy numbers of bearded
pigs, but their long-term survival there is not secure because of
ongoing forest loss and fragmentation, primarily for oil palm..020Downloaded from https://www.cambridge.org/core. Faculty of Classics, University of Cambridge, on 04 Dec 2017 at 12:41:45